A conventional technology in the above field is described in, for example, Japanese Patent Application Publication No. 2001-347227 (“the JP '227”). The JP '227 describes a vibration device used in a wireless communication terminal device such as a cell phone. The vibration device houses an oscillator including a permanent magnet inside a cylinder having a coil wound thereon. The oscillator moves reciprocatingly along a central axial direction of the cylindrical body, and generates vibration by striking strike-point members arranged at both ends of the cylinder.
However, in the vibrating device of the JP '227, the oscillator can move freely within the cylinder when the coil is in a non-conducting state. Hence, depending on the relationship between the position of the oscillator when driving begins and the movement direction of the oscillator, the oscillator may sometimes fail to be moved by the leading signal component of the driving signal. In this case no vibrations are generated.
To solve this problem, it is the aspect of the present invention to provide a vibration actuator capable of reliably starting the vibration upon input of a driving signal.